Lexus stalls when hot.

[surfsup]

I have a lovely old Lexus LS400 (1995 Mark 3) that starts every time and runs beautifully for the most part. The only problem is, when I take it for a long run at motorway speeds, it's liable to stall when the car eventually comes to a stop. It always re-starts immediately. Any suggestions, please?

[stanleyman]

It is quite possibly fuel vaporising in the pipes due to the heat build up when you stop. Allow it to cool down a bit before you have to stop. There may be a mod for a heatshield.

[surfsup]

Thanks for your input stanleyman. Some more detailed info: As the car slows, naturally the revs begin to fall. This happens gradually over a few seconds. However, instead of stabilising at normal idle speed, they soon begin to fall well below that and, while the car is still moving (and still in 'Drive') the engine just cuts out. (I've noted that sometimes - but not always - I can prevent a stall by switching on the A/C.) The really strange thing is that, as soon as I restart it, (and presumably well before any cooling can happen) the engine then spins happily at normal idle speed and continue to run perfectly until the next time I hit a toll-booth or something. Does this description still fit with your diagnosis?

[stanleyman]

Presumably you have an ECU and fuel injection so it could be a sensor or the ECU needs some diagnostics. It could still be a vapour lock that only clears when it stops. Will it pickup from low revs or just die when put you foot down again?

http://www.carelect.demon.co.uk/merc.html

[stanleyman]

Search "ECU" if that doesn't work.